Looking directly at a planar surface poses an issue for a time-of-flight detector, such as a wide-angle LEDDAR™, because the same surface is located at many different distances from the detector. For example, for a detector mounted 40 ft high looking straight down at a 140° angle, the ground just below the detector is located 40 ft away, whereas a point on the edge of the detection zone is approximately 120 ft away from the detector. This is illustrated schematically in FIG. 1.
Therefore, an object entering the detection zone can only be discriminated in regards of its reflectance relative to the ground multiplied by the relative surface area it is occupying. In some applications, the surface ratio between the object to be detected and the illuminated zone renders the detection of the presence of the object complex using conventional methods.
There are many applications in which time-of-flight detectors are useful, for example to activate or deactivate systems depending on the presence/absence of an object such as a vehicle, a person, an animal, etc. Such presence-controlled systems include interior and exterior smart lighting; indoor climate control/automation; security and surveillance (presence/movement/location of people, vehicles, etc.); obstacle and collision avoidance systems for cars, trucks, vans and other vehicles including marine vehicles, aircrafts, trains, etc. and for heavy equipment with displaceable arms or sections; navigation systems for terrestrial, marine, aerial, rail vehicles; level and volume sensing for solids and liquids; objects, people and animal profiling; and proximity detection.
In these applications, it would be useful to discriminate objects based on their distance from the detector.